Capillary Pressure & Resistivity Measurements

Capillary Pressure and Resistivity System (PCRI)


Prediction of Oil and Gas Initially In Place (OIIP and GIIP) in a field or reservoir is one of the major challenges in the early phase of field development. Two very important pieces of information for this estimation are:

  1. The primary drainage capillary pressure curve, which gives the relationship between water saturation saturation and height above the water oil contact.
  2. The saturation exponent, which gives you the relationship between conductivity and water saturation. The saturation exponent is important for the transfer of electrical profile curves from electrical well logs, to saturation profiles.

Both these parameters can be measured in the porous plate capillary pressure set-up provided by RS Systems.

Our PCRI set-up is a computer controlled system for performing capillary pressure and electrical property measurements at using refined or reservoir fluids. Special oil and water-wet porous plates allow for both drainage and imbibition processes. The standard system comes in heating cabinets with room for 8 individual core holders. Temperature and pressure can be controlled for each cabinet individually. Maximum temperature for the standard unit is 100oC, and maximum confining pressure is 700 bar. High temperature cylinders are used to accurately control pore and differential pressures.

A complete unit normally consists of 4 to 8 individually controlled zones, giving a capacity of 32 to 64 parallel tests.


For a full reservoir condition unit, capable of performing the test with live reservoir fluids, the equipment is delivered, either with a X-ray system for saturation monitoring (ISSM), or individual acoustic separators for each core holder.  ISSM profiles are often essential in the evaluation of the representativity of a core sample after preparation (i.e. Swi establishment), and before it is selected for advanced reservoir conditions displacements.

For quality control and to secure equilibrium at the different steps, RS Systems strongly recommend to accompany all capillary pressure experiments with measurements of electrical properties, both due to the fact that this gives vital data for interpretation of well logs, but also due to the fact that resistivity is more sensitive to saturation changes than both the ISSM and volumetric measurements.


The system measures saturation as a function of capillary pressure, both drainage and imbibition. Standard procedure will also measure resistivity data as well as porosity and permeability as a function of overburden pressure when bringing the sample back to reservoir conditions.